Shell structure and method of constructing

ABSTRACT

Domed and cylindrical shell structures of interwoven lightweight strips of metal or other lightweight materials, and method of constructing such shell structures. Several weaving patterns are disclosed which provide requisite flexibility of woven strips to enable the weave to be formed into a desired configuration such as a domed roof or a cylindrical silo. These shells have high strength-to-weight ratios and inherently attenuate seismic vibrations to provide protection against earthquakes. The strips are interwoven on a flat surface at ground level and then hoisted into place. Modules of portions of the shell can be prefabricated and joined to other like modules at the job site to form the complete shell.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of shell structures used for thestructural side walls and roofs of buildings, and methods ofconstructing such shell structures.

2. Description of Related Art

For lattice-like structures comprising shell-type frames, use has beenmade of solid truss, rigid joint structural members and cage structuretype steel frames in which steel frame members are removably and fixedlyconnected to each other at respective intersection points, and necessaryportions of these steel frame members are tensioned by fastening rods.These structures must be assembled according to a predeterminedconfiguration, and, like the shell of the truss structure, havebasically little freedom in the formation of curved surfaces.

Structures of a type using cables are complicated and require means forfixing cables to roof members, or the like.

Conventional shells of the general solid truss structure require greataccuracy in the dimension of each member, and involve problems ofeconomic assembly.

The present invention provides improvements over such prior art shellstructures.

SUMMARY OF THE INVENTION

A shell structure according to the present invention utilizes elongatestrip members, preferably steel, which are relatively easy to bend andtwist, by weaving or interlacing the strip members in two or moredirections one on another or by providing connections equivalent toweaving or interlacing. The invention comprises two preferredconfigurations of structure: cylindrical and dome-like.

The respective elongate strip members cross each other orthogonally orobliquely to form a mesh. The intervals between aligned elongate stripmembers are determined in part out of consideration for ease ofinterlacing such that the relative positions between the strip membersare not largely disordered by the interlacing process.

The respective elongated strip members are overlaid one on another in aplanar fashion at respective intersection points, but are not requiredto be completely fixed to each other during fabrication. When elongatedstrip members are interlaced one with the other, some displacement orslippage is permitted at their intersection points both linearly andangularly.

The shell structure is fastened with hoop means on its periphery tomaintain a predetermined structural configuration, although selectedportions of the periphery of the shell structure need not be fastened tothe hoops. In order to prevent the shell structure in a set-up conditionfrom being deformed due to wind and/or earthquake, the respective jointsmay be fixed by bolts, braces may be used partially or wholly, ortension members, such as wire, may be used.

Other embodiments of the invention in lieu of weaving or interlacing areemployed when it is difficult to weave or interlace elongated stripmembers due to restrictions of quality or workability of the stripmembers. These embodiments simulate weaving or interlacing byutilization of various connecting means where the strips overlap, andare based on the same principle as the woven and interlaced embodiments,to accomplish essentially the same beneficial inventive results.

In addition to elongate flat metal strip members, such as strip steel,the use of reinforced plastic strips is also contemplated. Also,flange-like ribs may be provided on the edges of the strip members whichadd strength and rigidity to the structure without hindering the meansfor weaving the strip members. These ribs beneficially provide clearancespace for bolt heads and nuts where it is required to use threadedfasteners to secure overlapping strip members. One means of securing thestrip members in lieu of weaving is to secure each overlap of stripmembers by threaded fastener means. Another means of securing stripmembers in lieu of weaving is to secure short straps over theintersections of strip members. These straps may be secured by threadedfasteners, or by welding, and various combinations of straps may beused. Further, structures may be fabricated in which the elongate stripsare made of wood and the bonding straps are made of metal. In additionto orthogonal patterns of strips, three or more strips may be arrayed inother geometric patterns and secured either by weaving or by fasteningmeans.

By weaving or interlacing the elongate strip members on a flat surface,a shell covering such as a plastic film may be superposed over the stripmembers prior to forming the strip members into the desired finalconfiguration of the shell structure. With the shell covering in place,it is then possible to attach suitable hoisting means to selected medialportions of the woven strip members which can then be hoisted to thedesired height of the structure. The strip members will assume theapproximate intended configuration of the structure, whereinafter theconfiguration can be accurately obtained and stabilized by the use ofbraces and chord members subtending selected concave or undersideportions of the shell structure.

Because the woven or interlaced elongate strip members forming thelattice-like shell structure are able to slip and/or slightly rotate onewith respect to another of the strip members in overlappingrelationship, it is possible to form the shell structure as it is beingslowly hoisted from its flat base. When the strip members are steel,additional forming is possible because of the malleability of metals,and, in particular, the malleability of steel. Thus, the strip membersmay be plastically deformed, if necessary.

The shell structure may also be used as the form for a concrete overlayin addition to serving as means to reinforce the concrete. The shellstructure may be used in addition to, or in lieu of, concretereinforcing bars. It is another feature of the invention that when beingused as the form for a concrete structure, the form may be removed fromthe structure, after the concrete has sufficiently cured, by removingthe forming hoop or hoops.

In another embodiment of the invention, the shell structure may befabricated by preforming the elongate strip members into desired arcuateconfigurations by use of subtending chord members. The strip members arethen sequentially overlapped and secured together.

In summary, the features of the above-described embodiments of theinvention are as follows:

(1) Construction of desired curved surfaces.

Since the shell structure is formed by a plurality of strip memberswoven together to define a latticework, it adapts to change in thecurvature of the shell by slight angular changes in the lattice corners.Accordingly, the curved surface is reasonably approximated with slightadjustments of the lattice configuration. Also, since the latticerigidity is slight and the entire structure is flexible, a desiredcurved roof is obtainable without the necessity of defining preciselythe spatial positions of each lattice member and joint, such as isrequired with prior art rigid trusses.

(2) Dynamic features of lattice-type shell structure.

A dynamic characteristic of the inventive shell structure is that therigidity of the individual strip members is low and the entire structureis flexible. When this structure is deformed upon receiving a load, itdoes not experience the complicated stress conditions or the localstress concentrations inherent in rigid body structures such as trussesand truss joints.

An inplane force within the lattice work of the invention is balanced bythe expansion and contraction of the strip members constituting theshell to provide a simple stress condition. Since the strip members arenot rigidly fixed at their theoretical points of intersection, secondarystress accompanying the deformation is also slight.

Since the strip members themselves restrain outward deformation one withthe other at their intersection points, not only is the buckling lengthof a strip member shortened, but also the yield strength is preventedfrom being abruptly reduced. Also, should a strip member fail in stress,the stress after the buckling is redistributed throughout thelatticework.

The outward bending of flat and curved strip members is transmitted tothe peripheral portion of the structure due to the bending and twistingof the respective crossing strip members.

(3) Vibration attenuating performance.

When the restraining braces and chord members are few in number, thewhole structure becomes flexible, and is deformable due to wind and/orearthquake vibrations. However, a large vibration-attenuating effect isinherent in the structure due to the frictional contact of the stripmembers constituting the latticework of the structure. Accordingly, thisinherent friction is positively utilized for earthquake-proof design instructures such as silos, wherein some degree of beneficial deformationis acceptable.

The inventive shell structure and the method of construction accordingto the present invention are utilized for roofs of various kinds ofbuildings and/or building frames. The interwoven strip members functionlike a uniform plate having few stress concentrations, and areadvantageously utilized for weight reduction of large spans.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a large roof span structure showingschematically an embodiment according to the present invention;

FIG. 2 is a fragmentary perspective view of a preferred embodiment ofthe invention showing elongate strip members in a woven condition;

FIG. 3 is a fragmentary plan view of a preferred embodiment of theinvention showing elongate strip members woven in three directions;

FIG. 4 is a fragmentary plan view of a preferred embodiment of theinvention in which the elongate strip members are segmented and havecommon points of overlap secured by fastening means;

FIG. 5 is a fragmentary perspective view of a preferred embodiment ofthe invention in which overlay and underlay segmental straps usingthreaded fasteners define points of strip member overlap;

FIG. 6 is a fragmentary perspective view of an embodiment of theinvention similar to FIG. 5 showing a latticework of elongate stripmembers;

FIG. 7 is a fragmentary perspective view of another embodiment of theinvention in which elongate strip members are superposed one on anotherin superposed interlacing pattern;

FIG. 8 is a fragmentary perspective view of yet another embodiment ofthe invention showing a latticework of elongate strip members secured atpoints of overlap by threaded fasteners;

FIG. 9 is a fragmentary plan view of an embodiment of the invention inwhich the elongate strip members are of channel configuration;

FIG. 10 is a fragmentary, partially sectioned, side elevational view ofthe embodiment of the invention of FIG. 9;

FIG. 11 is a fragmentary, partially sectioned, edge elevational view ofthe embodiment of the invention taken along the line 11-11 of FIG. 10;

FIG. 12 is a fragmentary, partially sectioned, elevational view ofanother embodiment of channel elongate strip members used in theinvention;

FIG. 13 is a fragmentary, partially sectioned, elevational view of theembodiment of the invention taken along the line 13--13 of FIG. 12;

FIG. 14 is a perspective schematic illustration of a method ofconstructing the inventive shell structure;

FIG. 15 is a perspective schematic illustration of a method ofconstructing the inventive shell structure using chord members tosubtend arcuate portions of elongate strip members; and

FIG. 16 is a perspective view of an embodiment of the invention appliedto the construction of a silo-type building.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows an embodiment of the present invention applied to a shellstructure for the frame of a dome roof. Elongate strip members 2A and2B, formed of thin band steel sheet, are interlaced to form latticework,and the periphery of the latticework is restricted by a hoop 4 formed ofsteel material or the like serving to define the configuration of thebase of shell structure 1.

During fabrication of the shell 1, the strip members 2 are notmechanically secured together, but instead are interwoven on a flatsurface prior to being set up into a predetermined configuration. InFIG. 2, it is shown by the arrows A that some shifting between the stripmembers 2 at their intersection points is permissible. However, once thedome 1 is formed, in order to resist the deformation forces of windand/or earthquake, it is preferable that the intersection points 3 bepositively fixed by mechanical means, and/or the curvature configurationof the latticework interwoven strip members be maintained by the use ofbraces and/or chord members. Opposite ends of the members 2 on theperiphery of the shell structure 1 are fixed with bolts or welded to thehoop 4.

In a preferred method of fabricating the inventive dome structure, aplurality of elongate strip members 2 are interwoven on a planar surfaceto form a flat latticework. Next, as shown in FIG. 14, the centralportion and several other medial portions of the latticework aresuspended by a crane or raised from beneath the latticework to urge thelatticework into the desired curved configuration. The extremities ofthe strip members 2 are then secured to a hoop 4, whereby the shellstructure 1 having the predetermined curved configuration is completed.According to this method of construction, the shell structure is thenfixed at the strip member intersection points by bolts after the set-up,or the configuration thereof is maintained by utilizing braces, chordmembers or the like. In the case where the shell structure is utilizedfor the frame of a film roof, the strip members 2 are interwoven on theground and a film member is then placed over and secured to thecompleted latticework.

FIG. 3 shows the strip members 2A, 2B, and 2C interlaced in threedirections to form hexagonal spaces therebetween. Strip members 2A and2B are secured at intersection points 3 by fasteners 5. Strip member 2Cis unrestricted with respect to strip members 2A and 2B, therebypermitting some limited movement therebetween. It is also to be notedthat adjacent pairs of strip members 2A and 2B form equilateralparallelograms (rhombi), which permit shifting between the strip members2A and 2B, as shown by the dotted line parallelogram 5A. This relativemovement between the strip members permits the shell structure to beeasily formed into a desired curved configuration in accordance with theconcept of the invention. Thus the strip members are intended not onlyto bend, but also to shift laterally.

The geometry of the embodiment of the invention shown in FIG. 4 issimilar to that of FIG. 3, but the concept is different. In FIG. 3, thestrip members are continuous, extending unbroken from one point on thehoop 4 to a second point on the hoop. In FIG. 4, the strip members aremade from a plurality of short segments 6A, 6B, and 6C. The segmentscomprising strip members 6A and 6B, respectively, are butt-weldedtogether at 8 in sufficient number to provide relatively short lengthsof strips, which are interwoven together generally in the same manner asshown in FIGS. 2 and 3, to partially form a lattice module. Segments 6Care not joined together, but instead are added to the module in thearticulated manner shown in FIG. 4, and held in place by fasteners 7.Gaps 9 are provided between the butt ends of segments 6C to allow forexpansion and contraction in forming a predetermined curved surface.After the surface has been formed, segments 6C are then bolted togetherthrough preformed bolt holes 9a to form continuous strips extending toconnecting points on the hoop 4. These modules can be fabricated at thejob site and then assembled at ground level with the requisiteadditional modules necessary to form the complete latticework.

It will be noted that the fasteners 7 provide the necessary pivot pointsrequired for the flexing of the parallelograms formed by welded stripmembers 6A and 6B. This flexibility enables the interwoven netting ofstrip members to be conformed to the required curvature of the finisheddome. Thereafter strip segments 6C are fastened together by means ofpreformed bolt holes 9a which provide the necessary rigidity to thecompleted shell structure by preventing further flexing of theparallelograms formed by strip members 6A and 6B.

FIG. 5 shows an embodiment of the strip member connection with simulatedweaving. In this embodiment, the strip members 2A and 2B are notinterwoven, but are merely overlaid, whereby the intersection points 3are defined by cross-over straps 10A and 10B secured to strip members 2Aand 2B with bolts 11. As illustrated in FIG. 5, strip members 2A and 2Bare sandwiched between cross-over straps 10A and 10B in such a manner asto allow some sliding and pivotal movement between the A and Bcomponents. This sandwich-type junction is not necessarily used at allintersection points 3, but may be staggered so that only alternateoverlays of strip members, for example, may be secured with cross-overstraps 10A and 10B.

In the embodiment of FIG. 7, pairs of strip members 2A--2A and 2B--2Bare superposed and interwoven, wherein the upper of the 2B strips aresandwiched between pairs of 2A strips and the lower of the 2A strips aresandwiched between pairs of 2B strips. The intersection points 3 aredetermined by threaded fasteners 12. This embodiment of the inventionhas the same freedom of lateral and pivotal movement as the embodimentof FIG. 5, discussed hereinabove. This superposed form of interweavingstrip members greatly enhances the overall strength of the structurewhile losing none of the flexibility at the intersection points 3necessary for forming the desired arcuate shape of the structure.

The embodiment of FIG. 8 is the least complex of the preferredembodiments of the invention. Therein is shown a simple latticework ofstrip members 2A and 2B secured together with bolts 13, defining aplurality of parallelograms in which bolts 13 provide pivot points aboutwhich the parallelograms may flex. Broken lines L indicate theflexibility of the parallelograms. It is understood that it is thisflexure that permits the forming of the shell to a specifiedconfiguration.

While heretofore have been enumerated the embodiments of flat strips asthe strip members, use is also made of strip members 14 provided on bothwidthwise edges with U-channel-like ribs 15 as shown in FIGS. 9 through11. In this embodiment, the strip member 14 is somewhat less flexiblethan the flat strips in bending performance, but the additional strengthobtained with U-channel strips renders this embodiment preferable forroofs which must be capable of withstanding heavy loads, such asencountered in northern climates where snow load is a consideration.However, in addition to pivotal flexibility about bolt 16 shown in FIG.9, enlarged bolt hole 17, FIG. 11, allows for some lateral movementbetween channel strips 14A and 14B.

FIGS. 12 and 13 show a modification of the embodiment of FIGS. 9 through11, principally in that strip members 14a and 14b are I-channel stripsrather than the U-channel strips of FIGS. 9 through 11. The I flanges15a provide still additional roof load capacity when specified.Otherwise, the functioning of the embodiments of FIGS. 9 and 12 isessentially the same. Both flanges 15 and 15a provide recesses for theheads 16A and nuts 16B of bolts 16.

FIGS. 14 and 15 schematically illustrate steps of constructing thepreferred embodiments of the inventive domed shell. As shown in phantomin FIG. 14, strip members 2A and 2B have been interwoven and are in theprocess of being hoisted at a central intersection point 3 by anoverhead crane, or from beneath the strip members by mechanical jackmeans well understood by those skilled in the art. When stripextremities 2a and 2b reach the base hoop 4, they are secured to thehoop and the shell is stabilized. Depending on the rigidity of theinterwoven strip members, which varies among the embodiments of FIGS. 2through 13, the shell may not need further stabilization. However, withthe embodiments of the invention such as shown in FIGS. 2, 3, or 8,further stabilization may be desirable, depending on the end use of theshell. If so, the configuration of the shell may be further rigidifiedby the application of chord members 19 which are used to sequentiallysubtend consecutive arcs of curvature of the strip members 2A and 2B, asshown in FIG. 15.

FIG. 16 shows an embodiment of the shell structure according to thepresent invention applied to the side wall of a silo 20. According tothis embodiment, vertical strip members 21 and horizontal strip members22 are interwoven. Horizontal strip members 22 are formed into circularloops, and the end portions of vertical strip members 21 are fixed toupper and lower hoops 24A and 24B. Though not shown, the butt ends ofhorizontal strip members 22 are joined to each other by means of weldingor mechanical fasteners. The strip members make planar frictionalcontact with each other at intersection points 23, which providerigidity to the structure. Furthermore, the frictional forces developedbetween strip members 21 and 22 at intersection points 23 act toattenuate forces of seismic vibration, and therefore provide earthquakeprotection to the silo.

It will occur to those skilled in the art, upon reading the foregoingdescription of the preferred embodiments of the invention, taken inconjunction with a study of the drawings, that certain modifications maybe made to the invention without departing from the intent or scope ofthe invention. It is intended, therefore, that the invention beconstrued and limited only by the appended claims.

I claim:
 1. A shell structure comprising: a lattice-like frame having acircular base member, said frame being formed of a first plurality offlexible elongate strip members having opposite end portions, said firstplurality of elongate strip members being substantially in parallelalignment and arcuately shaped; a second plurality of flexible elongatestrip members having first and second opposite end portions, said firstend portions being secured to said base; said second plurality ofelongate strip members being substantially in parallel alignmentsubstantially normal to said first plurality of flexible elongate stripmembers, and said first plurality of flexible elongate strip membersbeing secured to said second plurality of flexible elongate stripmembers in a manner adapted to maintain the arcuate shape of said firstplurality of flexible elongate strip members.
 2. The shell structure ofclaim 1, including a circular member remote from said circular base, andsaid second end portions being secured to said circular member.
 3. Theshell structure of claim 1, wherein said first plurality of flexibleelongate strip members are interlaced with said second plurality offlexible elongate strip members.
 4. The shell structure of claim 1,wherein said first plurality of flexible elongate strip members areformed into complete circles; said second plurality of flexible elongatestrip members are linear; and said first and second plurality offlexible elongate strip members are secured together to define acylindrical shell structure.
 5. The shell structure of claim 1, whereinsaid second plurality of flexible elongate strip members are arcuatelyshaped, said second end portions are secured to said circular baseremote from said first end portions; and said first and said secondplurality of flexible elongate strip members are secured together todefine a domed shell structure.
 6. The shell structure of claim 1,wherein said first second plurality of flexible elongate strip membersare secured in a manner adapted to permit slippage therebetween.
 7. Theshell structure of claim 1, including structural chord means secured tothe concave sides of said arcuately shaped flexible elongate stripmembers to define and to maintain said arcuate shapes.
 8. The shellstructure of claim 1, wherein said flexible elongate strip members areprovided with flange-like stiffening ribs on opposite sides thereof. 9.The shell structure of claim 1, wherein said flexible elongate stripmembers are formed from strip material with an I-shaped cross section.10. The shell structure of claim 1, wherein each of said flexibleelongate strip members is provided with a cross-over strap secured atthe intersection of each pair of normally aligned intersecting flexibleelongate strip members adapted to permit limited slippage therebetween.11. The shell structure of claim 10, wherein said cross-over straps aresecured to one surface only of each of said flexible elongate stripmembers.
 12. The shell structure of claim 10, wherein said cross-overstraps are secured to opposite sides of each of said flexible elongatestrip members.
 13. The shell structure of claim 10, wherein saidlattice-like frame comprises a plurality of lattice-like, substantiallyidentical, modules of interwoven segments of elongate strip members, andmeans to secured said modules together to fabricate said shellstructure.
 14. The shell structure of claim 13, comprising a firstplurality of elongate strip segments of a first module adapted to bebutt welded to a first plurality of elongate strip segments of a secondmodule.
 15. The shell structure of claim 13, comprising a secondplurality of elongate strip segments of a first module, and means tointerconnect said elongate strip segments within said fist module and toconnect said elongate strip segments o said first module to a secondplurality of elongate strip segments of an adjacent second module. 16.The shell structure of claim 1, wherein said flexible elongate stripmembers of each plurality of flexible elongate strip members are securedin superposed pairs with intermittent spaces therebetween to receiveflexible elongate strip members of the others of said plurality offlexible elongate strip members to pass therethrough.
 17. The shellstructure of claim 16, including fastening means to secure saidsuperposed pairs of said flexible elongate strip members between saidintermittent spaces.
 18. The shell structure of claim 1, wherein saidfirst plurality of elongate strip members are comprised of elongatestrip segments butt welded together, end to end.
 19. The shell structureof claim 1, wherein said second plurality of elongate strip memberscomprise: a plurality of elongate strip segments longitudinally alignedand spaced apart; means to secure said elongate strip segments to saidfirst plurality of elongate strip members; and means to integrallysecure each of said plurality of said longitudinally aligned,spaced-apart, strip segments to form continuous elongate strip members.20. The shell structure of claim 1, wherein said first nd secondplurality of elongate strip members are interlaced to formparallelograms, and pivotal connecting means at the apices of saidparallelograms adapted to permit said parallelograms to partially openand close.
 21. The shell structure of claim 20, including means tostabilize said parallelograms from partially opening or closing.
 22. Theshell structure of claim 1, including a third plurality of elongatestrip members aligned substantially parallel and interlaced with saidfirst and second plurality of elongate strip members.
 23. The shellstructure of claim 22, wherein said first, second, and third pluralityof elongate strip members are arrayed to define hexagonal spacestherebetween.
 24. The shell structure of claim 22, wherein said first,second, and third plurality of elongate strip members are arrayed todefine triangular spaces therebetween.
 25. A shell structure comprising:a lattice-like frame forming a predetermined curved surface, said framebeing formed of elongate strip members overlaid in at least twodirections one on another in a planar fashion on respective intersectionpoints; and fastening means for restricting said elongate strip membersfrom relative displacement between said elongate strip members, theintersection points of said elongate strip members being restrained bysaid fastening means to thereby provide connections equivalent tointerlacing; said fastening means consisting of bolt means andcross-over strap disposed along one elongate strip member so as to spanthe intersection point of said strip members themselves; said one stripmember and said cross-over strap sandwiching the other elongate stripmember therebetween; and both ends of each of said cross-over stripbeing secured to said one elongate strip member by said fastening means.26. A shell structure comprising: a lattice-like frame forming apredetermined curved surface, said frame being formed of elongate stripmembers overlaid in at least two directions one on another in a planarfashion on respective intersection points; and fastening means forrestricting said elongate strip members themselves from relativedisplacement between said elongate strip members, the intersectionpoints of said elongate strip members being restrained by said fasteningmeans to provide connections equivalent to interlacing, wherein saidelongate strip members is provided on opposite longitudinal edges withflange like ribs.
 27. A method of constructing a shell structure havinga lattice like frame formed of elongate strip members overlaid oneanother in at least two directions in a planar fashion on respectiveintersection points, comprising the teps of:first, on the ground,overlaying the strip members in at least two directions one another in aplanar fashion on respective intersection points: then forming alattice-like flat plate so as to allow for the relative displacement andslight rotation in the inplane direction between the respective stripmembers on the respective intersection points; hanging up said flatplate on one or several spots of the intermediate portion thereof, whilemaking the peripheral portion of said flat plate to slide to apredetermined position; and then fixing the peripheral portion of saidflat plate to the predetermined position to thereby construct the frameof the shell structure having a predetermined curved surface.
 28. Aconstructing method of a shell structure according to claim 27, whereina film member constituting the shell surface is previously mounted onsaid shell members overlaid one another on the ground.
 29. Aconstructing method of a shell structure according to claim 18, whereinsaid respective strip members are secured by fastening means on therespective intersection points after the peripheral portion of said flatplate is made to slide to the predetermined position and then fixedthereto.
 30. A constructing method of a shell structure according toclaim 29, wherein predetermined intersection points out of saidrespective intersection points are interconnected through chord membersused for holding the configuration of the shell structure after theperipheral portion of said flat plate is made to slide to thepredetermined position and fixed thereto.
 31. A method of constructing ashell structure having a lattice-like frame formed of strip membersoverlaid one another in a plane fashion in at least two directions onrespective intersection points, comprising the steps of:setting up saidstrip members in at least two directions as being overlaid one anotherin a plannar fashion; then sequentially combining predetermined sectionsof said strip members through chord members; and then setting up theframe of the shell structure having a predetermined curved surface asforming the arcuate configuration with a predetermined radius ofcurvature in the predetermined sections.
 32. The method of constructinga shell structure having a lattice-like frame of flexible elongate stripmembers having opposite end portions, comprising the steps of:(a)positioning a first plurality of flexible elongate strip members inlinear parallel alignment on a flat surface; (b) positioning a secondplurality of flexible elongate strip members in linear parallelalignment in overlaid fashion on said first plurality of flexibleelongate strip members and substantially normal thereto; (c) securingsaid first plurality of flexible elongate strip members to said secondplurality of flexible elongate strip members so as to allow relativedisplacement and slight pivotal movement between adjacent members ofsaid first and second plurality of flexible elongate strip members; (d)securing the plurality of said flexible elongate strip members tohoisting means at a position intermediate said end portions; (e)hoisting with said hoisting means said flexible elongate strip membersvertically upward a predetermined distance; (f) securing said endportions to the periphery of a planar base of preselected configuration;(g) releasing said hoisting means from said plurality of said flexibleelongate strip members; and (h) permitting said plurality of saidflexible elongate strip members to assume an unsupported configuration.33. The method of claim 32, wherein said flexible elongate strip membershave convex and concave sides, and the step of securing structural chordmembers to said concave sides to stabilize said shell structure.
 34. Themethod of claim 32, including the step of interlacing said first andsecond plurality of flexible elongate strip members.
 35. The method ofclaim 32, including the step of securing said first and second pluralityof flexible elongate strip members with cross-over straps adapted tobridge normally intersecting flexible elongate strip members.
 36. Themethod of claim 32, including the steps of stabilizing said shellstructure and applying an exterior surface cover to said shellstructure.
 37. The method of claim 36, including the steps of applying afilm over said shell structure and applying an outer layer of roofingmaterial over said film.
 38. The method of claim 32, including the stepof selecting the lengths of said flexible elongate strip members so thateach member will assume an arcuate shape when secured to said peripheryof said planar base which complements the arcuate shapes of adjacentparallel and intersecting strips to define an arcuate dome-like shellstructure.